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nerdralph / ArduinoShrink

replaces Arduino AVR Core functions with smaller and faster versions
MIT License
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Micros() is not compiled in timeout-like loops #10

Open omonar opened 3 years ago

omonar commented 3 years ago

I use micro() function to timeout a do-while loop

// Originate timestamp
t1 = micros();

// Wait till data is there or timeout...
int cb = 0;
do {
  // Destination timestamp, well, sort of :)
  t4 = micros();
  if ((t4 - t1) > 1000 * 1000UL) {
    // timeout after 1000 ms
    return false;
  }
  cb = udp.parsePacket();
} while (cb == 0);

// We've received a packet, read the data from it
udp.read(packetBuffer, NTP_PACKET_SIZE); // read the packet into the buffer

which gets compiled to

    4982:   0e 94 f1 02     call    0x5e2   ;  micros()
    4986:   2b 01           movw    r4, r22; t1
    4988:   3c 01           movw    r6, r24
    498a:   84 e2           ldi r24, 0x24   ; 36
    498c:   94 e0           ldi r25, 0x04   ; 4
    498e:   0e 94 5d 18     call    0x30ba  ;  udp.parsePacket()
    4992:   89 2b           or  r24, r25
    4994:   d1 f3           breq    .-12        ;  0x498a
    4996:   40 e3           ldi r20, 0x30   ; NTP_PACKET_SIZE = 48
    4998:   50 e0           ldi r21, 0x00   ; 0
    499a:   b7 01           movw    r22, r14
    499c:   84 e2           ldi r24, 0x24   ; 36
    499e:   94 e0           ldi r25, 0x04   ; 4
    49a0:   0e 94 14 18     call    0x3028  ;  udp.read(packetBuffer, NTP_PACKET_SIZE)

so it seems that the timeout check is not compiled in.

The same fragment of code without ArduinoShrink library compiles to

    4abe:   0e 94 2a 03     call    0x654   ;  micros()
    4ac2:   4b 01           movw    r8, r22; t1
    4ac4:   5c 01           movw    r10, r24
    4ac6:   0e 94 2a 03     call    0x654   ;  micros()
    4aca:   6b 01           movw    r12, r22; t4
    4acc:   7c 01           movw    r14, r24
    4ace:   2b 01           movw    r4, r22
    4ad0:   3c 01           movw    r6, r24
    4ad2:   48 18           sub r4, r8
    4ad4:   59 08           sbc r5, r9
    4ad6:   6a 08           sbc r6, r10
    4ad8:   7b 08           sbc r7, r11
    4ada:   f1 e4           ldi r31, 0x41   ; 65
    4adc:   4f 16           cp  r4, r31
    4ade:   f2 e4           ldi r31, 0x42   ; 66
    4ae0:   5f 06           cpc r5, r31
    4ae2:   ff e0           ldi r31, 0x0F   ; 15
    4ae4:   6f 06           cpc r6, r31
    4ae6:   71 04           cpc r7, r1
    4ae8:   08 f0           brcs    .+2         ;  0x4aec
    4aea:   72 c0           rjmp    .+228       ;  timeout has passed (exit)
    4aec:   8d e2           ldi r24, 0x2D   ; 45
    4aee:   94 e0           ldi r25, 0x04   ; 4
    4af0:   0e 94 c2 1a     call    0x3584  ;  udp.parsePacket()
    4af4:   89 2b           or  r24, r25
    4af6:   39 f3           breq    .-50        ;  0x4ac6
    4af8:   40 e3           ldi r20, 0x30   ; NTP_PACKET_SIZE = 48
    4afa:   50 e0           ldi r21, 0x00   ; 0
    4afc:   b8 01           movw    r22, r16
    4afe:   8d e2           ldi r24, 0x2D   ; 45
    4b00:   94 e0           ldi r25, 0x04   ; 4
    4b02:   0e 94 79 1a     call    0x34f2  ;  udp.read(packetBuffer, NTP_PACKET_SIZE)

I compiled it with the most recent version (1.8.16) of Arduino IDE and standard settings.

nerdralph commented 3 years ago

Thanks for the report. I haven't downloaded 1.8.16 yet, so I'll see if something changed from 1.8.13.